Method for producing a carnosic acid-rich plant extract

ABSTRACT

A carnosic acid-rich plant extract can be produced by extracting a dried and comminuted plant material containing carnosic acid with supercritical CO 2  at a pressure of at least 200 bar and at a temperature of at most 100° C. In a first step, super-critical CO 2  in a quantity of 10 to 50 kg of CO 2  per kg of plant material is passed through the plant material to obtain a first CO 2  extract. In a second step, additional supercritical CO 2  is passed through the plant material to obtain a second CO 2  extract, and a carnosic acid-rich plant extract is separated from the second CO 2  extract by lowering the pressure.

The invention is directed to a method for producing a carnosic acid-richplant extract by extracting a carnosic acid-containing plant materialwith supercritical CO₂.

Carnosic acid is a plant ingredient which can be used in foods orcosmetics as a natural antioxidant instead of the antioxidantsbutylhydroxyanisol (BHA) and butylhydroxytoluene (BHT) often usedhitherto. For such a use, carnosic acid-rich plant extracts are requiredwhich have a low intrinsic color and a low content of odor- andtaste-imparting substances and which should contain as little solvent aspossible.

EP 454 097 discloses methods for producing carnosic acid-rich extractswith a low content of essential oils from rosemary or sage. For this,either a two-stage extraction with supercritical CO₂ at firstly 300 to350 bar and 35 to 40° C. and then 500 bar and 40° C. is carried out, orextraction at 500 bar and 40° C. with supercritical CO₂ is carried outand, from the resulting CO₂ extract, one extract at a time isprecipitated fractionally in two pressure stages at firstly 115 to 120bar and 75 to 85° C. and then 33 to 35 bar and 10 to 17° C. The methodproduces extracts with a content of carnosic acid of more than 25% byweight, although they are still greenish-brown in color. The method hasthe disadvantage that it is necessary to work at different pressurestages and that during a separation in two pressure stages the viscousextract obtained in the first pressure stage is poorly separable fromthe still supercritical CO₂-rich phase.

DE 43 06 303 discloses methods for obtaining plant oils by extractionwith supercritical CO₂, in which the CO₂ extract is passed undersupercritical conditions over a bed of bleaching earth in order toremove colorings.

The invention provides a method for producing a carnosic acid-rich plantextract which involves an extraction of a dried and comminuted carnosicacid-containing plant material with supercritical CO₂ at a pressure ofat least 200 bar and a temperature of at most 100° C. During thisextraction, in a first step, supercritical CO₂ is passed through theplant material in an amount of 10 to 50 kg of CO₂ per kg of plantmaterial, giving a first CO₂ extract, in a second step, furthersupercritical CO₂ is passed through the plant material, giving a secondCO₂ extract, and a carnosic acid-rich plant extract is precipitated fromthe second CO₂ extract by lowering the pressure.

The method according to the invention produces a plant extract with ahigh content of carnosic acid and does not have the disadvantages of themethod known from EP 454 097.

In the method according to the invention, a dried and comminutedcarnosic acid-containing plant material is extracted. Preferably, aplant material is used which is dried to a water content of less than10% by weight. All drying methods known from the prior art can be usedfor drying the plant material. Preferably, the drying takes place attemperatures of less than 100° C., particularly preferably at less than85° C. The plant material is preferably dried in uncomminuted formand/or with the exclusion of atmospheric oxygen in order to avoid areaction of carnosic acid present therein with atmospheric oxygen duringthe drying. The plant material is used in comminuted form for theextraction. Preferably, the plant material is comminuted to aweight-based average particle size of less than 1.5 mm. All comminutionmethods known from the prior art can be used to comminute the plantmaterial. Preferably, the comminution takes place at temperatures ofless than 40° C. The plant material is preferably comminuted with theexclusion of atmospheric oxygen in order to avoid a reaction of carnosicacid present therein with atmospheric oxygen during the comminution.

Suitable carnosic acid-containing plant materials are plant parts ofplants from the family of the Labiatae, preferably plant parts of plantsof the genera Rosmarinum and Salvia. The plant material particularlypreferably comprises leaves of rosemary (Rosmarinum officinalis) or sage(Salvia officinalis).

The dried and comminuted carnosic acid-containing plant material isextracted in the method according to the invention with supercriticalCO₂ at a pressure of at least 200 bar and a temperature of at most 100°C. The temperature during the extraction must be more than 31° C. sothat the CO₂ is in the supercritical state. Preference is given toextracting at a pressure of 280 to 1000 bar and particularly preferablyat a pressure of 280 to 420 bar.

Suitable autoclaves for an extraction with supercritical CO₂ are knownto the person skilled in the art from the prior art. Preferably, for theextraction, supercritical CO₂ is passed through a layer of carnosicacid-containing plant material. The supercritical CO₂ here can be passedthrough the layer of plant material either in up-flow or down-flow. TheCO₂ here can be used either in pure form or mixed with up to 10% byweight of an entrainer known from the prior art. The entrainers used arepreferably aliphatic alcohols having up to four carbon atoms, alkaneshaving up to six carbon atoms and aliphatic ketones having up to fivecarbon atoms. However, extraction without entrainer is preferred.

In the method according to the invention, in a first step, thesupercritical CO₂ is passed through the plant material in an amount of10 to 50 kg of CO₂ per kg of plant material, giving a first CO₂ extract.In a second step, further supercritical CO₂ is then passed through theplant material, giving a second CO₂ extract. Preferably here, further 80to 250 kg of CO₂ per kg of plant material are passed through the plantmaterial. Preferably, in the second step, the supercritical CO₂ ispassed through the plant material at the same pressure as in the firststep. A carnosic acid-rich plant extract is then precipitated from thesecond CO₂ extract by lowering the pressure. An oil-rich plant extractcan be precipitated from the first CO₂ extract by lowering the pressure.Preferably, when lowering the pressure, the end pressure and the endtemperature are chosen such that the CO₂ changes from the supercriticalstate to the gaseous state. Suitable separators for precipitating theplant extract by lowering the pressure are known to the person skilledin the art from the prior art in respect of extractions withsupercritical CO₂.

Compared with the isolation of a carnosic acid-rich plant extract by thetwo-stage lowering of the pressure known from EP 454 097, the methodaccording to the invention has the advantage that a carnosic acid-richplant extract with a smaller proportion of essential oils is obtainedwhich has a reduced odor.

In a preferred embodiment of the method according to the invention, thesecond CO₂ extract is passed through a solid absorbent undersupercritical conditions prior to precipitating the plant extract.Absorbents which can be used here are all absorbents with whichcolorings co-extracted from the plant material can be absorbed.Preferably, the absorbents used are activated carbon, bleaching earth(Fuller's earth), kieselguhr, silica gel or cellulose. As absorbent,particular preference is given to using a bleaching earth which consistsof a calcium-containing bentonite or a calcium-containingmontmorillonite. Suitable bleaching earths are available from Südchemieunder the trade name Tonsil®. The absorbent can be used in powder formor preferably as granules. This embodiment can be used to producedecolored carnosic acid-rich plant extracts.

The CO₂ extract is preferably passed through the solid absorbent underthe same pressure and temperature conditions as for the extraction. Theextraction and the passing through the absorbent can take place inapparatuses separate from one another or in the same apparatus.

Preferably, the first CO₂ extract is also passed through the solidabsorbent before the oil-rich plant extract is separated off by loweringthe pressure in order to also obtain the oil-rich plant extract indecolored form. The first CO₂ extract and the second CO₂ extract can bepassed here separately from one another through the same absorbent orthrough different absorbents. Preferably, however, the first CO₂ extractand the second CO₂ extract are passed in succession through the samesolid absorbent.

In a particularly preferred embodiment, the carnosic acid-containingplant material and the absorption material are arranged in an autoclavein the form of superimposed layers and the supercritical CO₂ is passedfirstly through the layer of plant material and then through the layerof absorption material. If the supercritical CO₂ is passed here throughthe layer of plant material in up-flow, a layer of absorption materialis arranged above the layer of plant material. If the supercritical CO₂is passed through the layer of plant material in down-flow, a layer ofabsorption material is arranged underneath the layer of plant material.This embodiment has the advantage that a decolored carnosic acid-richplant extract can be obtained in an extraction plant known from theprior art for extraction with supercritical CO₂ without furtherpurification equipment or purification steps.

The example below illustrates the invention without, however, limitingthe subject matter of the invention.

EXAMPLE

1 kg of rosemary needles dried to a water content of 8% by weight andground to an average particle size of less than 1.5 mm are placed in theextraction container of an extraction autoclave. A layer of 100 g ofTonsil® Optimum 210 FF bleaching earth is applied onto the bed of groundrosemary needles. Supercritical CO₂ is then passed in up-flow throughthe bed at a pressure of 280 bar and a temperature of 65° C. The CO₂extract obtained is initially fed to a first separator in which a firstplant extract is precipitated at a pressure of 45 bar and a temperatureof 35° C. After 30 kg of supercritical CO₂ had been passed through thebed, the CO₂ extract obtained was fed to a second separator in which asecond plant extract was precipitated at a pressure of 45 bar and atemperature of 35° C. In total, 100 kg of supercritical CO₂ were passedthrough the bed. In the first separator, 77 g of an aqueous phase and113 g of an orange-colored liquid plant extract were obtained whichcomprised 13% by weight of carnosic acid and 32% by weight of essentialoil. In the second separator, 48 g of a yellow viscous plant extractwere obtained which comprised 41% by weight of carnosic acid and lessthan 1% by weight of essential oil.

1-11. (canceled)
 12. A method for producing a carnosic acid-rich plant extract by extraction of a dried and comminuted carnosic acid-containing plant material with supercritical CO₂ at a pressure of at least 200 bar and a temperature of at most 100° C., said method comprising the steps of: a) in a first step, passing supercritical CO₂ through plant material in an amount of 10 to 50 kg of CO₂ per kg of plant material to give a first CO₂ extract; b) in a second step, passing further supercritical CO₂ through the plant material at the same pressure as in step a) to give a second CO₂ extract; and c) precipitating a carnosic acid-rich plant extract from the second CO₂ extract by lowering the pressure.
 13. The method of claim 12, wherein the plant material comprises leaves of Rosmarinum officinalis or Salvia officinalis.
 14. The method of claim 12, wherein extraction is carried out at a pressure of 280 to 1000 bar.
 15. The method of claim 12, wherein, in the second step, CO₂ is passed through the plant material in an amount of from 80 to 250 kg per kg of plant material.
 16. The method of claim 12, wherein an oil-rich plant extract is precipitated from the first CO₂ extract by lowering the pressure.
 17. The method of claim 13, wherein extraction is carried out at a pressure of 280 to 1000 bar.
 18. The method of claim 17, wherein, in the second step, CO₂ is passed through the plant material in an amount of from 80 to 250 kg per kg of plant material.
 19. The method of claim 18, wherein an oil-rich plant extract is precipitated from the first CO₂ extract by lowering the pressure.
 20. The method of claim 12, wherein the second CO₂ extract is passed through a solid absorbent under supercritical conditions prior to precipitating the plant extract.
 21. The method of claim 20, wherein the first CO₂ extract and the second CO₂ extract are passed in succession through said solid absorbent.
 22. The method of claim 20, wherein the absorbent is selected from the group consisting of activated carbon, bleaching earth, kieselguhr, silica gel and cellulose.
 23. The method of claim 20, wherein the absorbent is a bleaching earth selected from the group consisting of calcium-containing bentonites and calcium-containing montmorillonites.
 24. The method of claim 20, wherein the absorbent is used in the form of granules.
 25. The method of claim 20, wherein the plant material and the absorption material are arranged in an autoclave in the form of superimposed layers and the supercritical CO₂ is passed first through a layer of plant material and then through a layer of absorption material.
 26. The method of claim 20, wherein the plant material comprises leaves of Rosmarinum officinalis or Salvia officinalis.
 27. The method of claim 26, wherein the first CO₂ extract and the second CO₂ extract are passed in succession through said solid absorbent.
 28. The method of claim 27, wherein the absorbent is selected from the group consisting of activated carbon, bleaching earth, kieselguhr, silica gel and cellulose.
 29. The method of claim 27, wherein the absorbent is a bleaching earth selected from the group consisting of calcium-containing bentonites and calcium-containing montmorillonites.
 30. The method of claim 29, wherein the absorbent is used in the form of granules.
 31. The method of claim 29, wherein the plant material and the absorption material are arranged in an autoclave in the form of superimposed layers and the supercritical CO₂ is passed first through a layer of plant material and then through a layer of absorption material. 